The holes in the flatbed make it seem like there's supposed to be something you can put on the back. I found a couple online that look similar - Maybe there were different accessories you could put on the back?
I think I had a road grader. Then, they expanded the neighborhood by adding a link road...and I crawled all over the machines on the weekends. One time, the workers were there and I got a ride-along on a big Caterpillar. Impressed the hell out of my 9-yr-old self!
After that, I was no longer interested in toy trucks.